Field of the Invention
The present invention relates to an image capturing apparatus and a driving method for an image sensor.
Description of the Related Art
On-board and monitoring image capturing apparatuses are generally required to have wide dynamic range performance. In addition, digital still cameras and digital video cameras have been required to have wide dynamic range performance. Under the circumstances, there is known a method of generating an image having a wide dynamic range by combining an image with a short exposure time and an image with a long exposure time.
Meanwhile, many of light sources such as LED light sources and fluorescent lamps blink in synchronism with commercial power supply. For this reason, if performing image capturing with a short exposure time, a light source which appears lit to the human eye is sometimes captured so as not to appear lit in a still image. In addition, the light source is sometimes captured to look rapidly blinking on a moving image.
Japanese Patent Laid-Open No. 2007-6049 discloses a technique of detecting the fluctuation cycle of a light source by using a fluctuation detection unit for detecting the energy fluctuation cycle of illumination. An overall exposure period is decided in accordance with this fluctuation cycle. This exposure period is alternately divided into effective and ineffective exposure periods at a predetermined ratio. There is disclosed an image capturing apparatus configured to acquire an image with a short exposure time in accordance with the fluctuation cycle of a light source by converting only charges, of the charges accumulated by an image capturing unit, which have been accumulated during effective exposure periods into an electrical signal.